Objective: To determine whether body size and perceived figure, both current and historical, are associated with a diagnosis of endometriosis on laparoscopy.[unreadable] [unreadable] Design: Cohort study of consecutively identified patients undergoing laparoscopy for tubal sterilization or as a diagnostic procedure.[unreadable] [unreadable] Setting: Two university-affiliated hospitals.[unreadable] [unreadable] Patient(s): A cohort of 84 women ages 18-45 years. Endometriosis was visualized in 32 cases; 52 women (controls) had no visualized endometriosis, including 23 undergoing tubal sterilization and 30 with other gynecologic pathology.[unreadable] [unreadable] Main Outcome Measure(s): Body mass index (kg/m2) from self-report and perception of body figure were compared for their ability to predict case status (diagnosed endometriosis), using logistic regression models. Longitudinal trends in BMI based on perceived figure at 5-year intervals from age 15 years were compared using mixed linear models.[unreadable] [unreadable] Results: Based on self-report, women diagnosed with endometriosis were taller, thinner, and had a significantly lower BMI. In this series, cases were more likely to be late maturers (menarche ?d 14 y) and late to initiate sexual activity (?d 21 y), while they were less likely to be gravid, parous, and a current smoker. Adjusting for age (in years), being tall (height ?d 68 in), and parity (yes, no), a higher current BMI was statistically protective for a diagnosis of endometriosis, regardless of whether BMI was determined by self-report (adjusted odds ratio [AOR]=0.88, 95% confidence interval [CI] 0.79-0.99) or from perceived figure (AOR=0.86, 95% CI 0.75-0.99). For every unit increase in BMI (kg/m2), there was an approximate 12-14% decrease in the likelihood of being diagnosed with endometriosis. In an adjusted repeated measures model, BMI was 21.3 ?b 0.6 kg/m2 (estimate ?b SE) for women with endometriosis, compared with 23.2 ?b 0.4 kg/m2 for the controls, a difference over all ages of !V1.9 ?b 0.8 kg/m2 (P = .045). This is a consistent difference of about 10 lb at every age, assuming an average height of about 64.5 in.[unreadable]